Repeatably and reliably lifting a heavy object requires a sturdy and well-built mechanism that must also be economical to produce. The vehicle towing industry requires tow truck mounted lifting mechanisms. One function of a tow truck's lifting mechanism is to lift an end of a vehicle and enable its transport without damage to the vehicle. A shortcoming in previous tow truck lifting mechanisms lies in their requirement of significant force to lift the vehicle. Therefore, a need exists for a lifting apparatus that is mountable on a tow truck and employs a mechanism for mechanical lift, to achieve vehicle lifts more effectively, using less force. Other industries, where heavy objects are routinely lifted, would also benefit from a method and apparatus that provides an improved lifting mechanism.
The structural support of known lifting mechanisms presents additional problems. For instance, in tow trucks, much of the weight of the towed vehicle must be supported by the lift mechanism. The transfer of this weight to the frame of the tow truck, through a system of hinges and pivots, challenges the structural strength of the lift mechanism. A shortcoming of currently used lift mechanisms is the poor balance between light weight and high strength. This is especially true in the new "wheel-lift" towing mechanisms, which have been developed to minimize damage to the towed vehicle and facilitate the extraction of the vehicle from a parallel parking space. Typically, wheel-lift towing mechanisms require a boom leg to be extended beneath the vehicle to be towed. The wheels of the vehicle are then attached by a wheel carriage assembly connected to the free end of the boom leg. The boom leg is then lifted or tilted and the vehicle is extracted without damage. Current wheel-lift systems with heavy booms, hinges and actuators, which are strong enough to lift heavy vehicles over years of steady use, are too heavy for the typical tow truck. Conversely, light weight lift mechanisms tend to be unreliable for the day-to-day rigors required in tow truck operation, or are simply unable to perform heavier lifts. Mechanical failures of these light weight mechanisms, from fatigue upon weight bearing members, are common. Therefore, a need exists for a lifting apparatus better able to structurally support the weight of the towed vehicle, efficiently transfer that weight to the frame of the tow truck and perform reliably over the life of the towing vehicle.
Tow trucks are typically retro-fitted with lift mechanisms. A lift mechanism manufacturer receives a tow truck at its factory, where the lift mechanism is added. The customization of a truck to receive a lift mechanism is a difficult task, requiring expert technicians. To simplify the installation and retro-fitting of a tow truck with the lift mechanism, the lift mechanism must be compact and also accommodate the frame configuration of the truck. A needs exists for a compact lift mechanism that accommodates the frame configuration of a tow truck and is especially suited for a retro-fit installation.